Mortuary + Realmwalker + Cryptic Trilobite

Mortuary

Realmwalker

Cryptic Trilobite

How it works

1. Cast Cryptic Trilobite either from your hand or from the top of your library by paying 0.
2. Cryptic Trilobite enters the battlefield and dies as a state-based action due to having zero toughness.
3. Mortuary triggers, putting Cryptic Trilobite on top of your library from your graveyard.
4. Repeat.

This loop turns the battlefield into a revolving door for Cryptic Trilobite, which arrives with zero toughness and immediately succumbs to state-based actions whenever you cast it. Mortuary catches the dying automaton and neatly places it back on top of your library every single time. Meanwhile, Realmwalker's changeling nature lets it claim every creature type, granting you the ability to peer into the future and continuously recast Cryptic Trilobite right off the top of your library.